The ratio is to do with the length of the index and ring finger. If someone has a small index finger and a long ring finger, the ratio is low. If they have a long index finger and a shorter ring finger, the ratio is high.

The difference is believed to be related to the amount of male hormones – mostly testosterone – the baby has been exposed to in the womb. The smaller the ratio, the more male hormones.

The latest findings suggest this difference can affect how men behave towards women.

Participants were asked to fill out forms for every social interaction that lasted for more than five minutes for 20 days. They used a check list of behaviours they engaged in, which scientists classified as either agreeable or quarrelsome.

Men with small digit ratios had about a third more agreeable behaviours and a third less quarrels than those with a large ratio. Lead author Debbie Moskowitz said: "When with women, men with smaller ratios were more likely to listen attentively, smile and laugh, compromise or compliment the other person."

Findings showed that men behaved in this way both in sexual relationship and with female friends and colleagues. The men with smaller ratios were also less argumentative with women.

In comparison, men with larger ratios were equally quarrelsome with both men and women. A woman's digit ratio had no effect on behaviour.

Previously, scientists had found men with a smaller digit ratio tended to have more children – something the study findings could help explain.

"Our research suggests they have more harmonious relationships with women; these behaviours support the formation and maintenance of relationships with women," Moskowitz said.

Researchers now plan to look at how male dominance, or competition with other men, varies according to digit ratios.

Study co-author Simon Young added: "It is fascinating to see that moderate variations of hormones before birth can actually influence adult behaviour in a selective way."